Novel apparatus to measure the low-permeability and porosity in tight gas reservoir

• We develop an apparatus which measure low-permeability and porosity simultaneously.
• The apparatus can also measure bi-directional permeability efficiently.
• We measure the rock properties of Gyeongsang tight sand using the apparatus.
• The geological features of the tight sand core are analyzed by Microfocus X-ray CT.
• The developed apparatus shows good result in measurements accuracy.

This study proposes a new apparatus which can simultaneously measure the physical properties such as low-permeability and porosity in a tight gas reservoir. The apparatus can also measure bi-directional permeability efficiently. The measurement of bi-directional permeability is designed in consideration of flow direction which can cause different results by heterogeneity. Using the apparatus, the experiments have been carried out to measure the low-permeability and porosity of three tight sand core samples which are from Gyeongsang sedimentary basin in Korea. As the results, the porosity ranges from 5.63% to 11% and the permeability measured in forward and reverse direction is 0.0004 md and 0.0005 md for TS-1, 0.0007 md and 0.0011 md for TS-2, and 0.0062 md and 0.007 md for TS-3, respectively. To investigate the effect of geological characteristics inside core sample on rock properties, X-ray scan of the core samples was taken by Microfocus X-ray CT. Obviously, the value of permeability and porosity are subject to geological features such as micro-crack. This means that the micro-crack plays an important factor in terms of permeability variation by its direction and length in a tight gas reservoir. For verification of measurement accuracy, regression analysis was carried out using the dimensionless pseudo-pressure between the measured data and analytical model. As the results, it is shown that both are approximately equal in terms of permeability and porosity.